When performing the wall surface cooling of a combustion chamber in a gas turbine combustor, cooling is performed by cooling grooves provided on the inside of the wall surface of the combustion chamber, and thus an increase in the temperature of the wall surface is suppressed.
Since the wall surface of the combustion chamber is cooled by the cooling grooves in this manner, if the temperature of the wall surface rises and the concentration of premixed gas in the combustion chamber become high, the combustion on the wall surface, that is, the wall surface combustion is generated. Then, if such wall surface combustion is generated, a flashback is generated in which a flame goes back toward the upstream side from the downstream side on the wall surface where the flow velocity of the premixed gas is low. Since air and fuel in the premixed gas are not sufficiently mixed with each other on the upstream side of the combustion chamber, when a flame reaches the upstream side due to the flashback and combustion on the upstream side is generated, NOx is generated.
Further, in a case where in addition to main combustion at the position of the inside in a radial direction of the combustion chamber, the wall surface combustion as described above is generated at the same axial position as the main combustion, heat generation concentration is generated at the axial position. In addition, since the wall surface combustion is unstable, large inner-pressure fluctuation occurs inside the combustion chamber depending on the presence or absence of the generation, and thus there is a concern that combustion oscillation may occur.
Here, in Patent Document 1, there is disclosed an acoustic liner that is provided on the outer peripheral surface of a combustion chamber, thereby performing combustion oscillation damping. Then, it is conceivable to form an air film on the wall surface of a combustion chamber by supplying purge air to acoustic holes of the acoustic liner as a method to prevent the above-described wall surface combustion by suppressing an increase in the temperature of a wall surface.